This invention relates to protective devices for a structure installed in a large body of water, such as a drilling and production platform installed in the open sea.
Large drilling and production platforms are known and used at the present time to either explore for oil or gas or to recover oil or gas from a known hydrocarbon producing structure. One form of these platforms is the type that is supported on the sea bed and is held in place by its own weight. Because these structures are located in the open sea they are subject to the hazards of this environment including the possibility of being struck by large floating objects such as vessels or ships or, depending on the area where the platform is located, icebergs or ice flows. The possibility of being struck by a large floating object is particularly great when bad weather conditions prevail, which conditions may cause heavy seas. Because many people may live and work on a large drilling platform, it is recognized that steps must be taken to protect this personnel from the serious danger for loss of life or grave injury if the platform should be struck by a large floating object.
Protective devices for platforms installed in the open sea have been proposed in the past and are known. According to these known devices, the kinetic energy of an iceberg impact is absorbed by means of frictional forces generated between the surfaces of a foundation and the underlaying surface of a protective body. A significant disadvantage of these known devices is that after displacement e.g. by an iceberg impact the protective body must be lifted up by deballasting and brought to a target position by winches or other suitable mechanical equipment. Subsequently, the protective body has to be put into its initial position by ballasting. To perform its protective function it is necessary that the upper edge of the protective body, which is in an idle position, extend above the level of the water.
Another solution proposed and known is a design which takes the huge loads affecting the platform by an impact by respective masses of the structure.
The present invention provides an improved protective compliant device for a structure, such as a platform, installed offshore which device has a protective body that helps prevent dangerous impacts from floating objects such as icebergs or ships by thrusting the latter aside and away from the structure. In addition to preventing an impact between the floating object and the structure, the protective body is able to slide back on its own to its initial position without any mechanical auxiliary equipment. The preferred protective device disclosed herein surrounds the structure on all sides and thus is able to protect the structure from a floating object approaching the structure from any direction.
According to one aspect of the present invention, a protective device for a structure installed in a large body of water includes a massive protective body capable of surrounding the structure to be protected and having a bottom with at least one inclined bearing surface. There are also bearing means for slidably supporting the protective body and these bearing means have at least one inclined bearing area adapted to engage slidingly the bearing surface. In addition, foundation means support the bearing means. When the protective device is struck by a floating object, the kinetic energy of the impact pushes the protective body upwards on the at least one bearing area from an initial position to an elevated position, and the kinetic energy is transformed into potential energy of the elevated body. The protective body with its received potential energy is capable of sliding back to its initial position after the impact and of thereby keeping the floating object away from the structure.
According to a further aspect of the invention, a protective device for a structure installed in a body of water includes a protective body capable of surrounding the structure to be protected and having a bottom with inclined bearing surfaces. Bearing means having inclined bearing areas adapted to engage sliding the bearing surfaces movably support the protective body.
Further features and advantages will become apparent from the following detailed description when considered in conjunction with the accompanying drawings.